Orthopaedics Flashcards
How is non-inflammatory, inflammatory, septic and haemorrhagic arthritis quickly distinguished on joint aspirate?
> 50’000 WCC’s or >75% neutrophils is highly suggestive of septic arthritis even if gram stain -ve
What is the conversion between WBC/mm3 to WBC/uL for joint aspirate analysis?
The same
2000/mm3 = 2000/uL
What is the sensitivity of a Gram stain of synovial fluid for bacteria?
29-50%
Thus a postive gram stain rules septic arthritis in but a negative one cannot rule it out
Which micro-organisms are unlikely to be seen on synovial fluid gram stain?
Mycoplasma
Mycobacteria
Fungi
Also early in the infection normal organisms may not be seen
When should septic arthritis still be suspected even if the gram stain is negative and crystals are present?
If the PMN ratio is >75%
If the WCC/mm3 or uL is >20,000
If the patient is clinically presenting as septic
What are the risk factors for septic arthritis?
Penetrating trauma/recent surgery to the joint
Poorly controlled diabetes
IVDU
Immunosuppression
Pre-existing arthritis in the joint (including gout)
Overlying soft tissue infection
Advanced age
Indwelling catheters
What are the most common organisms causing septic arthritis?
Staph aureus (most common)
Strep pneumoniae
Pseudomonas aeruginosa (immunosuppressed and IVDU)
Polymicrobial (trauma)
N. gonorrhoea (Active STI)
Mycobacteria/Fungi (immunosuppressed, indolent course)
Viral (Rubella, Dengue, Ross River, usually polyarthritis)
What is the Gustilo-Anderson classification for open fractures?
What is the Weber classification for ankle fractures?
In open wounds exposed to sea water, what organisms should be covered and with what agent?
Vibrio species
Doxycycline or Azithromycin or Ciprofloxacin
What is the basic management of an open fracture?
Clean the site (water +/- antiseptic)
Analgesia
Prophylactic ABx (Cefazolin etc)
Sedate then reduction
Plaster immobilisation
Keep elevated
Refer to orthopaedics for ORIF
What should always be assessed with fractures and dislocations?
Distal arterial pulses
capillary refill
Sensation and nerve function
Signs of compartment syndrome
How are upper limb nerve injuries quickly assessed for if injury below the elbow?
Radial- wrist drop, snuff box paraesthesia
Median- Lateral hand sensation, thumb abduction, ok sign
Ulnar- Medal hand sensation, finger abduction
What other structures are commonly injured with a tibial plateau fracture?
Medial collateral ligament
Meniscus on same side
What are the risk factors for achilles tendon rupture?
Male sex (5:1)
Older age
Sport (recreational 80% cases)
Flouroquinolone use
Glucocorticoids
Obesity
Pre-existing achilles tendinopathy
What is Thompsons test for achilles tendon rupture?
With the patient lying prone with feet over the end of the bed, squeeze the gastrocnemius and the foot should plantar flex
If does not plantar flex then suggestive of complete tendon rupture
What is the management of an achilles tendon rupture?
Complete- RICE, analgesia, place in below knee back slab with partial plantar flexion (equinus cast), refer to orthopaedics (surgical vs conservative Mx)
Partial- RICE, analgesia, CAM boot, outpatient ortho follow up
What are the risk factors for ACL tear?
Female
Younger age
High level sport
Sport whilst fatigued
Trauma/contact sport
What are the best physical exam tests for ACL injury?
Lachmans test- Knee 30 degrees flexion, pull tibia anteriorly, increased translation compared to normal side
Anterior draw test- Knee 90 degrees flexion, pull tibia anteriorly while sitting on the foot, increased translation compared to normal side
How is ACL tear diagnosed and what is the treatment?
MRI is the gold standard
RICE, analgesia, crutches and non-weight bearing
Refer to orthopaedics for consideration of surgery vs conservative management
What are the potential complications of a knee (tibiofemoral) dislocation?
Peroneal nerve injury
Popliteal artery injury
- thrombosis, tear, pseudoaneurysm
Meniscal injuries
Cruicate ligaments (posterior 1)
Collateral ligaments
Compartment syndrome
DVT
Joint instability
OA
Chronic pain
How is a tibiofemoral knee dislocation relocated?
What is the “pucker/Dimple/buttonhole” sign with tibiofemoral dislocation and what is its significance?
Pathognomonic of posterolateral tibiofemoral dislocation
A dimple or invagination of the tissue at the distal anteromedial thigh
Posterolateral TF dislocations are irreducible with closed reduction, and attempts to reduce in this fashion increase the risk of skin necrosis
What is the typical test used to test median nerve function with a supracondylar fracture?
Get patient to make an ok sign with their thumb and index finger
What is the common nerve injury with (peri)lunate dislocation/fracture?
Median nerve at the wrist
Causes loss of thumb aBduction
What are the general features of a posterior cruciate ligament rupture?
- Much larger ligament so needs strong force
- Usually have associated injuries (hip injuries, dislocated etc)
- Associated with blows to the leg when knee is flexed (ie falling onto flexed knee)
What is the mortality of hip fractures in the elderly?
10% 1 month
25% at one year
50% 3 years
How effective are the Ottawa knee rules?
100% sensitive, 40% specific
Reduced xray rates by approx 25-30% in adults and children without missing any fractures
What is a segond fracture and what is its significance?
A small avulsion fracture of the proximal/lateral tibia
75% have associated ACL injuries and almost all have meniscus tears
What are the risk factors for osteomyelitis?
Diabetes
Immunosuppression
IVDU
ATSI
Peripheral vascular disease
Sickle cell disease
Underlying metal wear
Iatrogenic (post procedure)
What are the imaging modalites for osteomyelitis?
Xray
- low specificity/sensitivity
CT
- Rapid and easy, pre-op planning
MRI
- best sensitivity, gold standard, also high negative predictive value
- Can detect 3-5 days after infection has started
- Beware of non-MRI compatable metallic ortho implants
Nuclear med
- When MRI contraindicated and too much artefact on CT (ie metalwear)
How dow you calculate an ankle brachial index (ABI)? What about an arterial pressure index (API)
ABI
- Lie the patient supine
- Take SBP in both arms
- Take SBP from the posterior tibial artery and the dorsalis pedis artery, use the higher number of the 2
API
- Place doppler over the artery
- Inflate cuff to 20mmHg beyond when the trace cuts off
- Release the cuff slowly, when the doppler signal comes back this is the SBP for that limb
- Do the same thing and compare with the affected limb
R) ABI/API = Highest pressure in R) foot / highest number from both arms
ie if R) brachial = 115, L) brachial = 110, R) dorsalis pedis = 80 and R) posterior tibial = 75
ABI = 80/115 = 0.7
Generally a ratio of <0.9 = arterial insufficiency
What is the Garden classification system for fractures of the neck of femur?
Predicts the development of osteonecrosis, most commonly used but only applies to subcapital fractures
Garden 1- Undisplaced and incomplete impacted fractures
Garden 2- Undisplaced complete
- Garden 1 and 2 are stable and treated with internal fixation
Garden 3- Complete and partially displaced
Garden 4- Complete fracture and completely displaced
- Garden 3/4 unstable and treated with arthroplasty
What are the different types based on position of femoral neck fractures? What is the important line that should be assessed on XR
Intracapsular
- Capital
- Subcapital (see Garden classes)
- Transcervical
Extracapsular
- Intertrochanteric
Subtrochanteric
What is the Salter-Harris classification of physeal fractures?
Indicates worsening prognosis with higher grade injuries
- Type 1/2 often treated conservatively with a cast and reduction
- Type 3/4/5 often need surgery
